Sprocket drive tensioning mount for conveyors

ABSTRACT

A chain-type conveyor forming a continuous loop of chain is driven by a large sprocket wheel which may be several feet in diameter. Tension is applied to the chain at one side of the wheel and accordingly a slack condition may occur at the other side of the wheel. The wheel is mounted along with its power drive, such as an electric motor, in a framework having a pivot point on the tension side of the wheel so that as the wheel revolves the tension side of the wheel will tend to be swung in a direction opposite to that in which tension is furnished to the chain, as a matter of reaction. This causes the opposite side of the wheel to swing in the opposite direction thereby taking up slack in the chain leaving the wheel at that side. The distance from the pivot point about which the mounting frame of the wheel can swing to the adjacent periphery is considerably shorter than the distance from the pivot point to the opposite side of the wheel so that only such torque as is necessary for taking up slack will be provided. Means are provided for telescopic movement of the conveyor guide and chain tracks to compensate for tensioning movement of the sprocket wheel mount. On carousel tray sorters where large sprockets are required to provide tray clearance, considerable space is saved and sorter length reduced by eliminating the need for a separate takeup loop. Additionally, the construction permits convenient initial tensioning of the chain by means of a weight bias acting on the mount.

United States Patent Mar. 7, 1972 Neal [54] SPROCKET DRIVE TENSIONINGMOUNT FOR CONVEYORS [72] Inventor: Warren D. Neal, Walkersville, Md.

[73] Assignee: Aerojet-General Corporation, El Monte,

Calif.

[22] Filed: June 11, 1970 21 Appl. No.: 45,403

[52] US. Cl ..l98/203, 198/208 [51] Int. Cl ....B65g 15/30, 1365b 23/02[58] Field of Search ..l98/203, 208; 74/242.l5 R

[56] References Cited Attomey-Edward O. Ansell, Albert M. Zalkind and D.Gordon Angus [57] ABSTRACT A chain-type conveyor forming a continuousloop of chain is driven by a large sprocket wheel which may be severalfeet in diameter. Tension is applied to the chain at one side of thewheel and accordingly a slack condition may occur at the other side ofthe wheel. The wheel is mounted along with its power drive, such as anelectric motor, in a framework having a pivot point on the tension sideof the wheel so that as the wheel revolves the tension side of the wheelwill tend to be swung in a direction opposite to that in which tensionis furnished to the chain, as a matter of reaction. This causes theopposite side of the wheel to swing in the opposite direction therebytaking up slack in the chain leaving the wheel at that side. Thedistance from the pivot point about which the mounting frame of thewheel can swing to the adjacent periphery is considerably shorter thanthe distance from the pivot point to the opposite side of the wheel sothat only such torque as is necessary for taking up slack will beprovided. Means are provided for telescopic movement of the conveyorguide and chain tracks to compensate for tensioning movement of thesprocket wheel mount. On carousel tray sorters where large sprockets arerequired to provide tray clearance, considerable space is saved andsorter length reduced by eliminating the need for a separate takeuploop. Additionally, the construction permits convenient initialtensioning of the chain by means of a weight bias acting on the mount.

20 Claims, 11 Drawing Figures PATENTEUMAR H972 I 3,647,050

sum 1 or 6 INVENTOR WARREN 0. NEAL WMf ATTORNEY PATENTEDMAR 7 1972 SHEET2 UF 6 PATENTEDHAR 1 me In nr no r71 m a:

SHEET 3 OF 6 FIG.3

PATENTEDMAR 7 I972 3, 647. 050

sum 5 OF 6 m wE SPROCKET DRIVE TENSIONING MOUNT FOR CONVEYORS Briefly,the invention comprises a fixed base frame, generally mounted at anelevation above a floor as on pedestals. The frame supports a drivesprocket wheel and mount means therefor, for automatically tensioning achain passing around the wheel and which chain motivates a series oftiltable trays in a conveyor system. The overall system of a tray typeconveyor of the kind in which the present invention is usable is shownin assignees previously filed application of Wooten, Neal, and Einfeldt,Ser. No. 2,638, filed Jan. I3, 1970. However, the invention disclosedherein is of general application in any chain drive system.

The invention herein utilizes components such as a carriage whichcarries the sprocket wheel and is rollably mounted on the fixed base sothat it can be biased as by a weight to maintain predetermined minimumtension in the sprocket chain driven by the wheel. The wheel is mountedon the carriage by a mounting means which comprises a pivotal framehaving a hearing which rotatively supports the wheel and which framealso carries the electric motor and gear reduction for the wheel. Apivotal connection is provided intermediate the wheel carrying frame andthe carriage which pivotal connection has an axis much closer to theupstream or tension side of the wheel then to the downstream or slackside of the wheel. The frame is suitably supported by rollers engagingthe carriage so that the frame can swing about the pivotal connectionand thus bodily carry the wheel to apply tension at the downstream sideof the sprocket chain in response to tension existing in the upstreamside.

A detailed description of the invention now follows in conjunction withthe appended drawing in which:

FIG. I is a plan view of the general layout of the sprocket wheel drivefor a tray conveyor of the carousel type;

FIG. 2 is an elevation taken generally through 22 of FIG. 1;

FIG. 3 is an elevation taken generally through 3-3 of FIG.

FIG. 4 is a plan view showing detailed structure of the pivoting mountmeans arrangement for the sprocket wheel;

FIG. 5 is an elevation showing essential elements as seen in FIG. 4,viewed in the same direction as the view in FIG. 2;

FIG. 6 is an end view again showing essential elements of the pivotalstructure viewed in the same direction as the view of FIG. 3;

FIG. 7 is an enlarged plan view of the downstream side of FIG. 1 showingthe articulation of the movable track assem'bly portion which curvesaround the sprocket wheel and is carried by the sprocket wheel mountmeans, and a portion of the fixed, i.e., stationary, track assembly;

FIG. 8 is a section through 88 of FIG. 7;

FIG. 9 is a section through 99 of FIG. 8;

FIG. I0 is a section generally through 10-10 of FIG. 7; and FIG. 11 isan end elevation thereof.

FIG. 10 is a section generally through 10-10 of FIG. 7, and FIG. 11 isan end elevation thereof through llll of FIG. 7.

In FIGS. I and 2 the invention is diagrammatically illustrated and willbe seen to comprise a fixed base 10 which supports a carriage 15 havinga pair of V groove rollers at one side and smooth surfaced rollers atthe other side. The V rollers 20 roll on inverted V tracks and thereforeeffect a fixed lineal guide for movement of the carriage, the tracksbeing suitably secured to the fixed base 10. The rollers 25 are simplyrolling supports for the other side of the carriage. The carriage hasreversible linear freedom of movement in the directions of arrow A.

A sprocket wheel mounting means comprising a frame which carriessprocket wheel bearing 38 is pivotally secured to the carriage as by apivotal connection pin means 40 and the axis P of such pivotalconnection is approximately one-tenth of the distance from the upstreamof tension side of the sprocket wheel W (shown in phantom in FIG. 1) asit is from the downstream or slack side 50, as measured on a diameternormal to the direction of freedom of the carriage 15. The

wheel mounting means 35 is supported for pivotal motion at one side onlyat the pivotal mount 40 and on its opposite side by rollers 55 rotativeon respective axes 46 and 47, in a horizontal plane, which pass throughthe vertical axis P of pivotal mount 40.

Accordingly, it can be seen that a counterclockwise swinging movement ofthe sprocket wheel mounting means 35 about axis P will bodily andpivotally carry the sprocket wheel on the arc indicated by arrow Bhaving P as its center, causing tension in the downstream side ofsprocket chain C. Such movement is caused by the load tension at theupstream side of the chain, the sprocket wheel rotating clockwise, arrowF.

The sprocket wheel is rotatively supported on mounting means 35 bybearing 38 having base disc 65 secured to the frame and the mountingmeans 35 also carries the electric motor 70 and gear reduction drive 75having drive sprocket 77, the sprocket wheel W being driven via thechain and coaxial sprocket 82 connected by collar 85. Base disc 65 ofbearing 38 is riveted or otherwise fastened to the framing of mountmeans 35, as later described, all as apparent in FIGS. 1 and 2. Thus,the entire assembly comprising the sprocket wheel and its motive powercomponents can pivot as a unit about axis P.

Sprocket chain C encompasses the wheel will the usual manner and cargotrays T may be connected as shown in Ser. No. 2,638.

In order to effect a predetermined minimum tension in the chain a cable93 (FIGS. 1-3) is attached to a weight 95 and connected to the mountingmeans 35 at 97, to bias the sprocket wheel in a direction leftward(FIGS. 1 and 2) to effect any desired amount of initial tension in chainC. The weight 95 is housed in a vertical chute 98, cable 93 passing overa pulley carried by the stationary components of a fixed support frame F(FIGS. 2 and 3). Portions of the fixed support are designated withground symbols for clarity.

From the above description it will be apparent that tension in theupstream side of the chain at point of entry 45 will cause bodilymovement of the sprocket wheel around the axis P in a counterclockwisedirection and this will effect a tension in the downstream side of thechain at 50 to maintain any degree of tension designed into the systemdependent upon the ratio of distances between axis P and the wheelperiphery measured to the points 45 and 50. Further, the cost of aconveyor sorter means in accordance with the invention is reduced due toreduction in sorter length by combining the drive and the sprocket chaintakeup into a single assembly as compared with a separate drive assemblyand a separate takeup assembly.

The various subassemblies indicated by the reference numerals l0, 15, 35and 40 are comprised of certain structural elements now to be generallydescribed. Thus, the pedestal base 10 has vertical column members suchas 105, suitably cross braced by members 107, as shown in FIG. 2, andcarrying parallel horizontal joists such as (FIGS. l-3) wherein eachjoist is suitably fastened at the top of a respective pair of columns105, such as by welding or the like. The joists carry guard hoods 112aand 11211 of channel iron over respective rollers 20 and 25. Pulley 100,over which the cable 93 for weight 95 passes, is secured to the web ofhood 1I2b via intermediate spacer channels 113.

Preferably the rollers 25 roll on wear strips 115 (FIG. 3) in the guardhoods, the hoods insuring against tilting of the sprocket wheel assemblyout of a substantially horizontal plane.

Each joist at its outer end (FIG. 2) has a coarse adjustment screw I20passing therethrough with a takeup nut 123 therefor; and each screwpasses through a respective bracket secured to the carriage 15.Accordingly, by adjusting the screws 120, the carriage 15 can be movedto the right as seen in FIG. 2 for permitting slack in the chain so asto remove chain links and/or trays when necessary. Both screws I20 areutilized for such purpose and takeup by means of the screws is theneffected after such work has been accomplished to place carriage 15 in afixed position during conveyor operation.

The carriage is supported on rollers by means of a longitudinal framemember 138 and also is supported on rollers by means of a parallellongitudinal framing member 144. The framing members are parallel tojoists 110 of the fixed frame, as seen in FIG, 1, and have stub axlesfor the rollers 20 and 25, as indicated at 146 (FIG. 1). Cross framemembers such as 148 and 152 connect the longitudinal frame members 138and I44 and are suitably welded therebetween. All frame members can bebars, channels or angle irons, etc., and member 144 is extended tosupport the outer end of a diagonally disposed cleat 154 having an angleiron segment 156 to support a roller 55 of mount means 35, segment 156also being secured to member 144, and the top edge of the angle ironflange supporting roller 55, as shown. Similarly, an angle iron segment156 supported across frame members 144 and 148 supports the other roller55.

The sprocket wheel mount comprises aligned track support tubular members160a and 16% transversely fastened to respective parallel longitudinaltubular framing members 170 having intermediate welded cross members180. Spacer bars 183 (FIG. 3) are secured on top of members 170 havingangle irons 185 and 185a on respective spacer bars, thus fastened to theframing members 170, and strongly braced with diagonal angle ironmembers, such as 190, between additional angle irons 185b, 1856 andcross member angle irons such as 185d and 1852, to form a rigid squareframe to which bearing base 65 is attached on members 190.

An electric motor and gear reduction drive support structure 210 issuspended between the frame members 170 (FIGS. l-3) comprised of aboxlike configuration having vertical angle irons such as 215,horizontal angle irons such as 220, diagonal bracing such as 225, andoutboard brace 228 secured to member 160b, all for the purpose ofeffecting very firm support for the motor 70 and gear reducer 75 viaplatforms such as 230 and 235 mounted on cross frame angle irons 240 and243 secured to the vertical angle irons.

Referring to FIGS. 4, 5 and 6, the structure for supporting pivotalmovement of the sprocket wheel mount means 35 is illustrated and inparticular FIG. 4 shows in plan the tubular member 160b extending fromthe longitudinal frame member 170 and braced by the diagonal member 270,which is fastened intermediate member 170 and member 16%. Furtherbracing is afforded by member 228 heretofore mentioned and shown inFIGS. 4, 5 and 6. A pair of plates 273 and 276, as seen in FIGS. 5 and6, are carried on gussets 280 and 284 wherein gusset 280 is suitablywelded intermediate members 138 and 276 and gusset 284 is also weldedbetween member 138 and member 276. The plate construction is thus verystrongly built in an all welded structure wherein plate 276 is welded tothe gussets and plate 273 is bolted as by bolts 288 to plate 276. Onplate 273, there is a thrust bearing 292 surmounting which is a plate294. Pivotally contiguous with plate 294 is a plate 300 which is weldedto the sprocket wheel mount 35, at the bottom of the diagonally disposedframe member 270 (see FIG. 1) and also at the bottom of the extendingframe member 16%. The frame member 270 is welded to the side of framemember 170 at one end and to frame member 16% at the other end. Thus avery strong triangular framework is provided for the plate 300 since itsupports one side of the swinging frame or mount means 35 via the thrustbearing 292. A bolt 310 passes through the plates and the thrust bearingto form,a pivot or pintle on which the entire mount means 35 can swingabout the bolt which effects the axis P.

The other side of mount means 35 is carried by rollers 55 on angle ironmembers 156, as heretofore mentioned, and as seen in FIG. 1, the rollersare carried on a frame member 170 by respective suitable welded outboardattached plate structure indicated generally at 315.

Inasmuch as the sprocket wheel mount means 35 swings on the bolt 310 asa pivot in order to increase tension in the chain, and further since itmay be necessary to slack off on both sides of the chain via screws 120for maintenance work,

it is desirable to provide some means of expanding or contracting theconnections between the bodily movable tracks that go around thesprocket wheel and move as the wheel is bodily moved, in relation to thefixed portion of the tracks leading to and coming from the sprocketwheel.

This is preferably arranged by mounting the sprocket wheel encompassingarcuate portions of the tracks on the sprocket wheel mount means 35 andproviding articulated sliding and/or pivotal connections to the fixedportions. Thus, referring to FIG. 1, the outsidemost arcuate track 350having stationery portion 350a is the equivalent of track 15 asdisclosed in Ser. No. 2,638 and is preferably a channel open at itsradial inner side for the outer wheels of the trays where it goes aroundthe sprocket wheel. It is supported vertically at the points marked withan X vertically thereabove at the ends of the frame members 170. It isalso supported at its ends at respective ends of frame members a and16%. The next outermost arcuate track 360 having stationary portion 360ais supported at the points marked X vertically thereabove on the framemembers lying directly therebelow, namely frame members 170, 160a and160b. This is the track for the actuator cam, i.e., the tray tiltingroller 132 shown in Ser. No. 2,638, FIG. 3. Thus, track 360 is theequivalent of track 35 in Ser.

No. 2,638 and is, as in the previous application, shown as a channelopen at the top for the tray actuator rollers to extend thereinto inorder to ensure that the trays will remain horizontal as they go aroundthe sprocket wheel.

The rigid connection between each tray and the drive chain is normallysufficient so that a plain flat track can be used for the outermosttrack, but a channel, open at the inner side is preferred to avoidpossible mishap if some unbalanced forces should cause the trays to rocktransversely in going around the sprocket wheel.

There is no need for any arcuate continuation of stationary track 380for the innermost wheels of the trays. As seen in Ser. No. 2,638 (FIG.la, tracks 10) track 380 stops short of the sprocket wheel at bothentrance and exit of the sprocket wheel. The innermost wheels simplypass over the sprocket wheel in going therearound, being unsupported,since the remainder of the tray, chain, and other structure issufiicient to hold the trays level along with their carriages.

The present invention provides for an actuation of telescopic joints forthe tracks at the upstream and downstream ends of the sprocket wheel, aswill be later described to ensure proper alignment of the tray wheelsand tray actuating roller to and from the sprocket wheel when thesprocket wheel swings with support means 35 in automatically tensioningthe chain.

The chain itself goes around the sprocket and therefore requires noguide.

Referring to FIGS 2 and 3, it will be noted that arcuate track 350 issupported on a combination of angle members generally designated as 385and 385a, as exemplary, which will be understood to be secured to framemembers 170, 160a and 160b, respectively. Track 360 rests on plates andangle iron supports generally designated as 390 and 3900 for support. Itwill be understood that angle iron support constructions just describedappear at the various points marked X on FIG. 1, and are only exemplary.It will likewise be understood that the stationary portions of the trackare supported in the conveyor loop in any suitable manner, e.g., as inSer. No. 2,638.

From the preceding it will be apparent that as the chain tension atpoint 45 on the sprocket wheel (FIG. 1) causes the entire sprocket wheel35 to bodily rotate around the axis P of the bolt 310, the arcuatetracks will swing around the same axis. However, the various rollers inthe arcuate tracks must enter and leave those tracks from and to thefixed track portions. Also, the innermost wheels of the trays shouldleave the respective fixed track portions and reenter thereon properlyaligned. While the need for pivotal and telescopic transition elementsneed not be essential for a workable conveyor system not of massiveconstruction nor for heavy-duty cargo handling, e.g., the simple arcuatetrack arrangement in Ser. No. 2,638 would be feasible without pivotaland telescopic track elements, the present invention provides suchelements where conveying systems are huge, trays are massive and cargoup to 300 pounds per tray is carried.

Referring to FIGS. 7-11, and reference being made to FIG. I for theoverall plan view, a description of the pivotal and telescopicarticulated connections between the movable arcu ate track portionsaround the sprocket wheel and the stationary portions at both sides ofthe wheel will now be explained as to such essentials thought novel sothat persons skilled in this art will readily understand theconstruction. The illustration is exemplary only and details of routinestructural engineering, fastenings, bracings, shimming, leveling, etc.,etc., are omitted as being conventional and matters of designers choiceand knowledge.

Inasmuch as the connections are the same at both sides of the sprocketwheel, being substantially mirror images of each other, only theconnections for the downstream side of the wheel will be described indetail, except that at the upstream side, as seen in FIG. 1, thearticulated connection later described for track 380 is supported onmember 270 instead of member 160b, but essentially the structures arethe same.

In FIGS. 1 and 7-I0 the Roman numerals I, II and III indicate pivotaltrack connections for, respectively, as shown in phantom in FIG. 9, theouter wheels WO of the trays, the tilting actuator rollers R of thetrays, and the inner wheels WI of the trays, in the generalconfiguration of Ser. No. 2,684, FIG. 10.

The pivotal connection I (FIG. 9) joins arm 400 comprised of angle iron(FIG. 8), having a surface plate 405 secured thereto, with the arcuatetrack 350. Thus, arm 400 is connected via a link 408 pivotally connectedto the arm 400 at 408a (FIG. 9) and to the arcuate track section 350 at408b. Wheels leaving track 350 will roll on plate 405 to the stationarytrack 350a, the pivotal structure being supported by welded or boltedangle iron construction secured to member 16011, e.g., angle iron pieces4090, 409b, 4090. The member 409C is welded to the bottom flange oftrack 350, and member 409a is welded to member 1600.

Pivot 408b is carried by angle iron member 4090. The entrance end oftrack 350a is supported on angle iron members such as 420, 4200, 425a,425b, the latter two being transversely carried by the framework supportof the conveyor in any suitable manner (not shown) to support trackstructure at the junctions. The horizontal flange of arm 400 slides onthe support surface comprising angle iron members 435a and 435b. Member435a extends from member 425a to a vertical column 400 and member 435 issecured to member 4350 (FIG. 8) via a spacer bar 4350 between thevertical flanges. The vertical flange of arm 400 can slide in thespacing 435d thus provided. The wheels WO actually roll through a dropof a small fraction of an inch due to the thickness of arm 400 and plate405 onto the horizontal flange of member 435a. The outboard comer ofmember 435a is carried on angle iron member 442 supported on member 425aand fitted into a notch of the end of a track segment 445 of track 3500to form a flush surface at 445a. The segment 445 can be a separate shorttrack for assembly convenience, as indicated by the additional abuttedflush joint 448 supported in angle iron 450 on member 425b.

The geometry of arm 400, link 408, plate 405, members 435a and 435b, andthe spacing 435d, will be understood to be such that regardless of anyswung position of sprocket wheel mount means 35, arm 400 will slide byreciprocal guidance in spacing 435d actuated via the link 408 withsliding movement on member 4350. Arm 400 is thus motivated by swingingof track 350 around axis P (FIG. I), to provide a path over which theouter wheels WO of the trays can run between the movable and thestationary track portions, 350 and 350a respectively.

In a similar manner the arm 460, the upstream counterpart of arm 400, islinkage connected with the upstream end of arcuate track 350 to effect apath over which the outer wheels of the trays can roll from thestationary to the arcuate movable track portion.

The pivot means Il (FIG. 9) intermediate the tray tilting roller guidechannel track components 360, 360a, comprises a pivot arm 465 pivoted tothe arcuate movable track portion 360 at 46511 and welded to a shorttrack section 470 at 465b so that it can slide upon actuation by arm 465as track 360 swings. A telescopic joint 475 effects alignment in anyposition of track section 470. The telescopic joint is provided byspaced angle irons 480 carried by members 425a and 425k. Sufficient playin the telescopic joint is provided so that even when the section 470 isin any angularly related position there will be no binding or jamming,section 470 being slidably movably supported on member 425a.

The pivot means III (FIGS. 7, 8 and l0) comprises a channel 486 (alsosee FIG. I) open at the outer side pivotally connected to the framemember 106a.

The pivotal structure comprises a pintle 497 carried between bars 497aand 4971) welded top and bottom, respectively, to member 1600 with anintermediate vertical plate 497e, welded therebetween and to member a.The pintle is pinned in place as shown, as by pins such as 497d and hasa rotative collar 497e therearound to which is welded a channel supportarm 497f extending downstream to a vertical brace 497q secured theretoand welded to channel 486 for support thereof.

The channel 486 leads to the telescopic joint 500 comprising two sets ofinterdigitated bars within one set, i.e., alternate bars 510, connect tothe fixed track portion 380 being spacedly welded thereon to ahorizontal flange 520. The other set of alternate bars 530 are spacedlywelded to the bottom flange 535 of the channel 486. The bottom flange535 is cut away from point 540 to the end of the channel 486 so that thetop edges of bars 510 can be flush with the flange 535 for smoothtransition of wheels WI. Bars 530 are slidably supported on flange 520and notched at 540 to be top flush with bars 510. Thus the two sets ofinterdigitated bars form an extensible and contractable flush tracksurface, flush with flange 535 and track 380, over which the innerwheels WI of the trays can roll from the channel 486. This type ofsliding bar joint is believed preferable as a telescopic connectionrather than the sliding plate joint 405 used for the outer wheelsbecause the flush surfaces of the bars and tracks provide a smoothertransition of the rolling wheels.

The spacing of the bars of each set is close enough to provide amplesurface support for the rolling wheels, and where the bar sets overlap,at about the center of the configuration, the wheel support surface hasno gaps except for the designed tolerance necessary to allow linearmovement of bars 530 upon actuation by pivot 497 as support means 35swings. The axis of pivot 497 is located (FIG. 1) so that the motionpath of bars 530 is practically tangential to sprocket wheel W and,accordingly, no significant angular motion of movable bars 530 is metwhich might cause undue friction or jamming in sliding relative to fixedbars 510.

The upstream side of sprocket wheel W has the same telescopic joint andpivot structures as I, II and III, just described the only difference ofany structural significance being that the support for the pivot of thetrack 380 is on member 270, the bars attached thereto which areequivalent to bars 497a and 497b, being shorter and angularly disposeddue to the geometry of the structure.

Depending upon the type of chain used, a chain guide upstream anddownstream of the sprocket wheel is desirable and such a guide has beenindicated in FIG. 7 at 560 for the downstream portion of sprocket wheelW. A chain guide such as 560 or any other types of chain guides may ofcourse be suitably secured to any fixed portion of the fixed tracksupporting structure or to one of the fixed tracks, as a matter orchoice and design.

From the foregoing, it will be apparent that the invention provides in aconveyor system a tak-up mechanism responsive to torque load wherein thedrive wheel, for example a sprocket wheel or a belt pulley, is bodilymoved by virtue of reaction force, It will be noted that the inventionis not necessarily restricted to tension type driven members such aschains, belts or the like, but could also be used in precisely the sameapplication of principle and substantially the same construction andarrangement for compression types of drive. This will be readilyapparent to persons skilled in the art, who will recognize that suitablerelocation of pivotal mount 40 effects slack take up at point 45(FIG. 1) when torque load reaction is applied at 50.

What is claimed is:

1. in a conveying system, a tensioning and slack takeup mechanism for achainor belt-type driven member comprising a horizontal drive wheel anddrive wheel mount means for said drive wheel effecting rotary supportfor said drive wheel and providing a vertical axis on which said drivewheel is rotative for exerting drive tension on a driven member; apivotal device having means whereby said drive wheel is bodily pivotalabout a vertical axis disposed at a predetermined distance from therotative axis of said drive wheel; whereby load tension force effectedon said drive wheel by a driven member at an upstream portion of saiddrive wheel effects bodily pivotal motion thereof about said pivotalaxis to increase tension and take up slack in said driven member at adownstream portion of said drive wheel; a chain around said drive wheelmotivated thereby in a horizontal plane and cargo-carrying membersconnected to said chain and driven thereby; including support means forsaid cargo carrying members disposed for support thereof in passingaround said drive wheel.

2. In a conveying system, a tensioning and slack take up mechanism for achainor belt-type driven member comprising a drive wheel and drive wheelmount means for said drive wheel effecting rotary support for said drivewheel and providing an axis on which said drive wheel is rotative forexerting drive tension on a driven member; a pivotal device having meanswhereby said drive wheel is bodily pivotal about an axis disposed at apredetermined distance from the rotative axis of said drive wheel;whereby load tension force effected on said drive wheel by a drivenmember at an upstream portion of said drive wheel effects bodily pivotalmotion thereof about said pivotal axis to increase tension and take upslack in said driven member at a downstream portion of said drive wheel;said system including track means having a track at least partiallyencompassing said drive wheel; means whereby said track is bodilymovable about said latter axis with said drive wheel; said track meansalso having a relatively fixed track extending from said mechanism;including actuatable track connection means disposed intermediate theencompassing track and the fixed track comprising an actuatingconnection coupled with said drive wheel so as to be actuated foreffecting a path between the encompassing track and the fixed track whensaid drive wheel has bodily pivotal motion.

3. ln a system as set forth in claim 2, said actuatable track connectionmeans comprising a telescopic joint joining the encompassing track withthe fixed track and having an intermediate track member havingsubstantially linear movement as said drive wheel is bodily pivoted.

4. In a system as set forth in claim 3, wherein said actuatingconnection comprises a pivotal joint; said pivotal joint being disposedwith respect to said drive wheel so as to exert approximately tangentialthrust in the direction of linear movement of said telescopic joint,said telescopic joint having sufficient transverse play to effectsubstantially linear movement at any angular orientation of said pivotaljoint.

5. In a system as set forth in claim 4, wherein said telescopic jointcomprises a pair of suitably spaced guide members fixedly secured tosaid fixed track, said track member being slidably disposed between saidguide members during bodily pivotal movement ofsaid drive wheel.

6. In a conveying system, a tensioning and slack takeup mechanism for achainor belt-type driven member comprising a drive wheel and drive wheelmount means for said drive wheel effecting rotary support for said drivewheel and providing an axis on which said drive wheel is rotative forexerting drive tension on a driven member; a pivotal device having meanswhereby said drive wheel is bodily pivotal about an axis disposed at apredetermined distance from the rotative axis of said drive wheel;whereby load tension force effected on said drive wheel by a drivenmember at an upstream portion of said drive wheel effects bodily pivotalmotion thereof about said pivotal axis to increase tension and take upslack in said driven member at a downstream portion of said drive wheel;including a fixed track for a tray to be motivated by said drivenmember; and means for connecting said fixed track to said pivotal devicecomprising a telescopic joint having a set of bars actuatably connectedthereto and interdigitated with a set of bars secured to said fixedtrack; and means supporting said sets of bars so that the top edgesthereof are substantially flush.

7. In a conveying system, a tensioning and slack takeup mechanism for achainor belt-type driven member comprising a drive wheel and drive wheelmount means for said drive wheel effecting rotary support for said drivewheel and providing an axis on which said drive wheel is rotative forexerting drive tension on a driven member; a pivotal device having meanswhereby said drive wheel is bodily pivotal about an axis disposed at apredetermined distance from the rotative axis of said drive wheel;whereby load tension force effected on said drive wheel by a drivenmember at an upstream portion of said drive wheel effects bodily pivotalmotion thereof about said pivotal axis to increase tension and take upslack in said driven member at a downstream portion of said drive wheel;said drive wheel mount means comprising a reciprocal carriage and saidpivotal device comprising a frame pivotally secured thereto, meansbiasing said frame in a direction to effect a predetermined tension in adriven member encompassing said drive wheel, said drive wheel beingcarried on said frame.

8. In a system as set forth in claim 7, said frame having support onsaid carriage at said pivotal means and coaxially therewith at one sideof said drive wheel and said frame having spaced roller means effectingroller support on said carriage at the other side of said drive wheel.

9. In a system as set forth in claim 8, wherein said predetermineddistance is closer to the upstream portion of said wheel than to thedownstream portion whereby an increment of bodily motion of said wheeleffected by tension in said driven member produces a larger increment ofmotion at the downstream portion of said wheel.

10. In a system as set forth in claim 7, including means for poweringsaid drive wheel comprising an electric motor, and said electric motorbeing carried by said frame.

11. In a conveying system, a tensioning and slack takeup mechanism for achainor belt-type driven member comprising a drive wheel and drive wheelmount means for said drive wheel effecting rotaty support for said drivewheel and providing an axis on which said drive wheel is rotative forexerting drive tension on a driven member; a pivotal device having meanswhereby said drive wheel is bodily pivotal about an axis disposed at apredetermined distance from the rotative axis of said drive wheel;whereby load tension force effected on said drive wheel by a drivenmember at an upstream portion of said drive wheel effects bodily pivotalmotion thereof about said pivotal axis to increase tension and take upslack in said driven member at a downstream portion of said drive wheel;said pivotal device comprising a drive wheel support structure having apivotal connection means for attachment to a relatively fixed member atan upstream side of said structure and having spaced support meanscomprising rollers at the downstream side of said structure and adaptedto roll on a relatively fixed surface, said rollers having axesintersecting the axis of said pivotal connection means.

12. In a conveying system, a tensioning and slack takeup mechanism for achainor belt-type driven member comprising a drive wheel and drive wheelmount means for said drive wheel effecting rotary support for said drivewheel and providing an axis on which said drive wheel is rotative forexerting drive tension on a driven member; a pivotal device having meanswhereby said drive wheel is bodily pivotal about an axis disposed at apredetermined distance from the rotative axis of said drive wheel;whereby load tension force effected on said drive wheel by a drivenmember at an upstream portion of said drive wheel effects bodily pivotalmotion thereof about said pivotal axis to increase tension and take upslack in said driven member at a downstream portion of said drive wheel;said mount means comprising a carriage supported for reciprocal motionand said pivotal device being carried thereon and pivotally connectedthereto; a base on which said carriage is movable for translating saiddrive wheel to effect initial tension in a driven member and forpositioning said drive wheel to effect slack in said driven member formaintenance work and the like; adjustable screw means intermediate saidcarriage and said base for effecting a predetermined positioning of saidcarriage; weight bias means connected to said pivotal device foreffecting bias on a driven member to exert tension therein; said weightbias device comprising a weight and a cable suspension therefor havingpulley support on said base.

13. In a conveyor system, a tensioning and slack takeup mechanism for achainor belt-type driven member comprising a drive wheel and drive wheeltorque responsive means providing rotary support for said drive wheel onan axis on which said drive wheel is rotative for exerting torque toeffect drive tension in a driven member; and providing support wherebysaid drive wheel is bodily pivotal about an axis disposed at apredetermined distance from the rotative axis of said drive wheel;whereby load tension force effected on said drive wheel by a drivenmember at an upstream portion of said drive wheel effects bodily pivotalmotion thereof about said pivotal axis to increase tension and take upslack in said driven member at a downstream portion of said drive wheel;wherein said driven member is for the motivation of a plurality of trayshaving side rollers and a tilt actuating roller; and arcuate channeltrack encompassing the rotational axis of said drive wheel for receivingouter rollers of trays in moving around said drive wheel; an inwardlydisposed arcuate channel track coaxial with said first mentioned channeltrack for receiving tray actuating rollers; said two tracks extendingsubstantially from an upstream to a downstream side of said drive wheel;respective fixed tracks for connection to said arcuate tracks; andconnection means for connecting said arcuate tracks to respective fixedtracks of a conveyor system, and means whereby said arcuate tracks arebodily pivotal with said drive wheel.

[4. ln a conveyor system as set forth in claim 13, including anadditional fixed track disposed at the upstream and downstream side ofsaid drive wheel and inwardly disposed of the aforementioned fixedtracks for receiving inner rollers of trays; said connection meansextending from said fixed tracks to said torque responsive means; saidconnection means comprising actuatable track segments to effect pathsfor all said rollers to and from said fixed tracks for trays passingaround said drive wheel.

15. In a conveyor system as set forth in claim 14, all said tracksegments having pivotal connection to said torque responsive means foractuation thereby and being telescopically connected to respective fixedtracks.

16. In a conveyor system, a drive wheel and a driven means motivatedthereby having a force receiving flight and a return flight; a pivotalmount for said drive wheel responsive to torque load on said drive wheelto bodily pivot said drive wheel in a direction to reduce slack in saidreturn flight; including a first track means connected thereto, saidfirst and second track means having relative motion when said drivewheel has pivotal movement; and connection means connecting said firstand second track means having relative motion with res pect to saidfirst and second track means to effect a continuing path therebetweenwhen relative motion between said first and second track means occurs.

17. In a conveyor system, a drive wheel and a driven means motivatedthereby having a force receiving flight and a return flight; a movablemount for said drive wheel responsive to torque load on said drive wheelto bodily move said drive wheel in a direction to reduce slack in saidreturn flight; including a first track means bodily movable with saiddrive means, and a second track means connected thereto, said first andsecond track means having relative motion when said drive wheel hasbodily movement; and connection means connecting said first and secondtrack means having relative motion with respect to said first and secondtrack means to effect a continuing path therebetween when relativemotion between said first and second track means occurs.

18. A pivotal device for carrying a drive wheel to be bodily pivoted inresponse to tension in a driven member at an upstream side, forincreasing tension in a driven member at a downstream side; track meansfixedly secured to and extending between the upstream and downstreamsides of said pivotal device; track means arcuately encompassing saidpivotal device and means effecting actuatable segmental track sectionsbetween said arcuate track means and respective fixed tracks affordingcontinuous paths for elements of trays motivated by said driven member,said track segments being connected to said pivotal device for actuationso as to effect said paths at any pivoted position of said pivotaldevice.

19. A tensioning device for a sprocket wheel, comprising a fixed base; acarriage on said base and moveable thereon to effect initial tension inchain means to be driven by said wheel; sprocket wheel support means onsaid carriage and a sprocket wheel rotatively carried by said supportmeans; a pivotal connection between said support means and saidcarriage; the pivotal axis of said pivotal connection being disposedoffside of the rotative center of said wheel whereby tension in a chainmeans entering said wheel causes pivotal movement bodily of said wheelaround said pivotal connection to maintain tension on said chain meansleaving said wheel.

20. [n a conveying system, a tensioning and slack takeup mechanism for achainor belt-type driven member comprising: a drive wheel and drivewheel mount means for said drive wheel effecting rotary support for saiddrive wheel and providing an axis on which said drive wheel is rotativefor exerting drive tension on a driven member; a pivotal device havingmeans whereby said drive wheel is bodily pivotal about an axis disposedat a predetermined distance from the rotative axis of said drive wheel;whereby load tension force effected on said drive wheel by a drivenmember at an upstream portion of said drive wheel effects bodily pivotalmotion thereof about said pivotal axis to increase tension and take upslack in said driven member at a downstream portion of said drive wheel,including telescoping track means for connection between said pivotaldevice and a fixed track of a conveyor system and comprising two sets ofinterdigitated relatively slidable bars; means whereby one set of saidbars has a pivotal connection with said pivotal device; means wherebythe other set of bars is secured to said fixed track; means supportingsaid sets of bars so that the top edges thereof are substantially flushand form a smooth transition path to said fixed track.

1. In a conveying system, a tensioning and slack takeup mechanism for achain- or belt-type driven member comprising a horizontal drive wheeland drive wheel mount means for said drive wheel effecting rotarysupport for said drive wheel and providing a vertical axis on which saiddrive wheel is rotative for exerting drive tension on a driven member; apivotal device having means whereby said drive wheel is bodily pivotalabout a vertical axis disposed at a predetermined distance from therotative axis of said drive wheel; whereby load tension force effectedon said drive wheel by a driven member at an upstream portion of saiddrive wheel effects bodily pivotal motion thereof about said pivotalaxis to increase tension and take up slack in said driven member at adownstream portion of said drive wheel; a chain around said drive wheelmotivated thereby in a horizontal plane and cargo-carrying membersconnected to said chain and driven thereby; including support means forsaid cargo carrying members disposed for support thereof in passingaround said drive wheel.
 2. In a conveying system, a tensioning andslack take up mechanism for a chain- or belt-type driven membercomprising a drive wheel and drive wheel mount means for said drivewheel effecting rotary support for said drive wheel and providing anaxis on which said drive wheel is rotative for exerting drive tension ona driven member; a pivotal device having means whereby said drive wheelis bodily pivotal about an axis disposed at a predetermined distancefrom the rotative axis of said drive wheel; whereby load tension forceeffected on said drive wheel by a driven member at an upstream portionof said drive wheel effects bodily pivotal motion thereof about saidpivotal axis to increase tension and take up slack in said driven memberat a downstream portion of said drive wheel; said system including trackmeans having a track at least partially encompassing said drive wheel;means whereby said track is bodily movable about said latter axis withsaid drive wheel; said track means also having a relatively fixed trackextending from said mechanism; including actuatable track connectionmeans disposed intermediate the encompassing track and the fixed trackcomprising an actuating connection coupled with said drive wheel so asto be actuated for effecting a path between the encompassing track andthe fixed track when said drive wheel has bodily pivotal motion.
 3. In asystem as set forth in claim 2, said actuatable track connection meanscomprising a telescopic joint joining the encompassing track with thefixed track and having an intermediate track member having substantiallylinear movement as said drive wheel is bodily pivoted.
 4. In a system asset forth in claim 3, wherein said actuating connection comprises apivotal joint; said pivotal joint being disposed with respect to saiddrive wheel so as to exert approximately tangential thrust in thedirection of linear movement of said telescopic joint, said telescopicjoint having sufficient transverse play to effect substantially linearmovement at any angular orientation of said pivotal joint.
 5. In asystem as set forth in claim 4, wherein said telescopic joint comprisesa pair of suitably spaced guide members fixedly secured to said fixedtrack, said track member being slidably disposed between said guidemembers during bodily pivotal movement of said drive wheel.
 6. In aconveying system, a tensioning and slack takeup mechanism for a chain-or belt-type driven member comprising a drive wheel and drive wheelmount means for said drive wheel effecting rotary support for said drivewheel and providing an axis on which said drive wheel is rotative forexerting drive tEnsion on a driven member; a pivotal device having meanswhereby said drive wheel is bodily pivotal about an axis disposed at apredetermined distance from the rotative axis of said drive wheel;whereby load tension force effected on said drive wheel by a drivenmember at an upstream portion of said drive wheel effects bodily pivotalmotion thereof about said pivotal axis to increase tension and take upslack in said driven member at a downstream portion of said drive wheel;including a fixed track for a tray to be motivated by said drivenmember; and means for connecting said fixed track to said pivotal devicecomprising a telescopic joint having a set of bars actuatably connectedthereto and interdigitated with a set of bars secured to said fixedtrack; and means supporting said sets of bars so that the top edgesthereof are substantially flush.
 7. In a conveying system, a tensioningand slack takeup mechanism for a chain- or belt-type driven membercomprising a drive wheel and drive wheel mount means for said drivewheel effecting rotary support for said drive wheel and providing anaxis on which said drive wheel is rotative for exerting drive tension ona driven member; a pivotal device having means whereby said drive wheelis bodily pivotal about an axis disposed at a predetermined distancefrom the rotative axis of said drive wheel; whereby load tension forceeffected on said drive wheel by a driven member at an upstream portionof said drive wheel effects bodily pivotal motion thereof about saidpivotal axis to increase tension and take up slack in said driven memberat a downstream portion of said drive wheel; said drive wheel mountmeans comprising a reciprocal carriage and said pivotal devicecomprising a frame pivotally secured thereto, means biasing said framein a direction to effect a predetermined tension in a driven memberencompassing said drive wheel, said drive wheel being carried on saidframe.
 8. In a system as set forth in claim 7, said frame having supporton said carriage at said pivotal means and coaxially therewith at oneside of said drive wheel and said frame having spaced roller meanseffecting roller support on said carriage at the other side of saiddrive wheel.
 9. In a system as set forth in claim 8, wherein saidpredetermined distance is closer to the upstream portion of said wheelthan to the downstream portion whereby an increment of bodily motion ofsaid wheel effected by tension in said driven member produces a largerincrement of motion at the downstream portion of said wheel.
 10. In asystem as set forth in claim 7, including means for powering said drivewheel comprising an electric motor, and said electric motor beingcarried by said frame.
 11. In a conveying system, a tensioning and slacktakeup mechanism for a chain- or belt-type driven member comprising adrive wheel and drive wheel mount means for said drive wheel effectingrotaty support for said drive wheel and providing an axis on which saiddrive wheel is rotative for exerting drive tension on a driven member; apivotal device having means whereby said drive wheel is bodily pivotalabout an axis disposed at a predetermined distance from the rotativeaxis of said drive wheel; whereby load tension force effected on saiddrive wheel by a driven member at an upstream portion of said drivewheel effects bodily pivotal motion thereof about said pivotal axis toincrease tension and take up slack in said driven member at a downstreamportion of said drive wheel; said pivotal device comprising a drivewheel support structure having a pivotal connection means for attachmentto a relatively fixed member at an upstream side of said structure andhaving spaced support means comprising rollers at the downstream side ofsaid structure and adapted to roll on a relatively fixed surface, saidrollers having axes intersecting the axis of said pivotal connectionmeans.
 12. In a conveying system, a tensioning and slack takeupmechanism for a chain- or belt-type driven member comprising A drivewheel and drive wheel mount means for said drive wheel effecting rotarysupport for said drive wheel and providing an axis on which said drivewheel is rotative for exerting drive tension on a driven member; apivotal device having means whereby said drive wheel is bodily pivotalabout an axis disposed at a predetermined distance from the rotativeaxis of said drive wheel; whereby load tension force effected on saiddrive wheel by a driven member at an upstream portion of said drivewheel effects bodily pivotal motion thereof about said pivotal axis toincrease tension and take up slack in said driven member at a downstreamportion of said drive wheel; said mount means comprising a carriagesupported for reciprocal motion and said pivotal device being carriedthereon and pivotally connected thereto; a base on which said carriageis movable for translating said drive wheel to effect initial tension ina driven member and for positioning said drive wheel to effect slack insaid driven member for maintenance work and the like; adjustable screwmeans intermediate said carriage and said base for effecting apredetermined positioning of said carriage; weight bias means connectedto said pivotal device for effecting bias on a driven member to exerttension therein; said weight bias device comprising a weight and a cablesuspension therefor having pulley support on said base.
 13. In aconveyor system, a tensioning and slack takeup mechanism for a chain- orbelt-type driven member comprising a drive wheel and drive wheel torqueresponsive means providing rotary support for said drive wheel on anaxis on which said drive wheel is rotative for exerting torque to effectdrive tension in a driven member; and providing support whereby saiddrive wheel is bodily pivotal about an axis disposed at a predetermineddistance from the rotative axis of said drive wheel; whereby loadtension force effected on said drive wheel by a driven member at anupstream portion of said drive wheel effects bodily pivotal motionthereof about said pivotal axis to increase tension and take up slack insaid driven member at a downstream portion of said drive wheel; whereinsaid driven member is for the motivation of a plurality of trays havingside rollers and a tilt actuating roller; and arcuate channel trackencompassing the rotational axis of said drive wheel for receiving outerrollers of trays in moving around said drive wheel; an inwardly disposedarcuate channel track coaxial with said first mentioned channel trackfor receiving tray actuating rollers; said two tracks extendingsubstantially from an upstream to a downstream side of said drive wheel;respective fixed tracks for connection to said arcuate tracks; andconnection means for connecting said arcuate tracks to respective fixedtracks of a conveyor system, and means whereby said arcuate tracks arebodily pivotal with said drive wheel.
 14. In a conveyor system as setforth in claim 13, including an additional fixed track disposed at theupstream and downstream side of said drive wheel and inwardly disposedof the aforementioned fixed tracks for receiving inner rollers of trays;said connection means extending from said fixed tracks to said torqueresponsive means; said connection means comprising actuatable tracksegments to effect paths for all said rollers to and from said fixedtracks for trays passing around said drive wheel.
 15. In a conveyorsystem as set forth in claim 14, all said track segments having pivotalconnection to said torque responsive means for actuation thereby andbeing telescopically connected to respective fixed tracks.
 16. In aconveyor system, a drive wheel and a driven means motivated therebyhaving a force receiving flight and a return flight; a pivotal mount forsaid drive wheel responsive to torque load on said drive wheel to bodilypivot said drive wheel in a direction to reduce slack in said returnflight; including a first track means connected thereto, said first andsecond track means having rElative motion when said drive wheel haspivotal movement; and connection means connecting said first and secondtrack means having relative motion with respect to said first and secondtrack means to effect a continuing path therebetween when relativemotion between said first and second track means occurs.
 17. In aconveyor system, a drive wheel and a driven means motivated therebyhaving a force receiving flight and a return flight; a movable mount forsaid drive wheel responsive to torque load on said drive wheel to bodilymove said drive wheel in a direction to reduce slack in said returnflight; including a first track means bodily movable with said drivemeans, and a second track means connected thereto, said first and secondtrack means having relative motion when said drive wheel has bodilymovement; and connection means connecting said first and second trackmeans having relative motion with respect to said first and second trackmeans to effect a continuing path therebetween when relative motionbetween said first and second track means occurs.
 18. A pivotal devicefor carrying a drive wheel to be bodily pivoted in response to tensionin a driven member at an upstream side, for increasing tension in adriven member at a downstream side; track means fixedly secured to andextending between the upstream and downstream sides of said pivotaldevice; track means arcuately encompassing said pivotal device and meanseffecting actuatable segmental track sections between said arcuate trackmeans and respective fixed tracks affording continuous paths forelements of trays motivated by said driven member, said track segmentsbeing connected to said pivotal device for actuation so as to effectsaid paths at any pivoted position of said pivotal device.
 19. Atensioning device for a sprocket wheel, comprising a fixed base; acarriage on said base and moveable thereon to effect initial tension inchain means to be driven by said wheel; sprocket wheel support means onsaid carriage and a sprocket wheel rotatively carried by said supportmeans; a pivotal connection between said support means and saidcarriage; the pivotal axis of said pivotal connection being disposedoffside of the rotative center of said wheel whereby tension in a chainmeans entering said wheel causes pivotal movement bodily of said wheelaround said pivotal connection to maintain tension on said chain meansleaving said wheel.
 20. In a conveying system, a tensioning and slacktakeup mechanism for a chain- or belt-type driven member comprising: adrive wheel and drive wheel mount means for said drive wheel effectingrotary support for said drive wheel and providing an axis on which saiddrive wheel is rotative for exerting drive tension on a driven member; apivotal device having means whereby said drive wheel is bodily pivotalabout an axis disposed at a predetermined distance from the rotativeaxis of said drive wheel; whereby load tension force effected on saiddrive wheel by a driven member at an upstream portion of said drivewheel effects bodily pivotal motion thereof about said pivotal axis toincrease tension and take up slack in said driven member at a downstreamportion of said drive wheel, including telescoping track means forconnection between said pivotal device and a fixed track of a conveyorsystem and comprising two sets of interdigitated relatively slidablebars; means whereby one set of said bars has a pivotal connection withsaid pivotal device; means whereby the other set of bars is secured tosaid fixed track; means supporting said sets of bars so that the topedges thereof are substantially flush and form a smooth transition pathto said fixed track.